Bathroom fans

Published on November 12th, 2015 | by Henri


Installing a bathroom exhaust vent

Q.  We are in need of installing an bathroom exhaust vent in our home.  The bathroom exhaust fan was installed by a contractor a couple of years ago and he vented it directly into the attic.  My question is whom should I contact to perform this work?  Should it be a handyman, roofer or who else could do this work for us ? Thank you for your time and help.

A.  I am always amazed at the number of stupid things some contractors will do out of ignorance. Dumping bathroom moisture in an attic is loading a cold attic with moisture it cannot handle. Condensation, frosting and mold are sure to take place. Eventually, structural damage can develop.
A competent contractor, electrician or experienced handy person should be able to extend the vent to the outside.

The best way to do so is to use a 4-inch diameter Schedule 20 PVC drain pipe, making sure that the bell end faces toward the fan side and not the outside. (The picture with this post shows an example of a bell-end pipe.) The pipe should be exhausting outside a gable wall as low as possible. It should not be vented through gable vents, ridge vents or soffit vents. It should terminate outside with a hooded wall jack. Avoid plastic louvered jacks; too many flaps break in harsh weather.

It is best to install the pipe with a slight pitch to the outside by using small blocks of diminishing size. Once the pipe is installed properly, it should be insulated by placing 4-inch-thick fiberglass batts snugly on each sides and on top.

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